Netbooting Microsoft Windows 7 and XP
Chris Holman∗
Centre for Advanced Internet Architectures, Technical Report 130226A
Swinburne University of Technology
Melbourne, Australia
[email protected]
Abstract—This tutorial shows how to set up Microsoft
Windows 7 and XP to be booted using network attached
storage. iSCSI support is built in to a Windows 7 installer
using the Windows 7 Automated Installation Kit. DHCP,
an iSCSI server and a TFTP server are configured on the
server to provide a PXE client and an iSCSI target. Once
set up, a client PC will be able to operate entirely without
a local disk.
Index Terms—Windows 7, Windows XP, PXE, netbooting
I. I NTRODUCTION
PXE (“Preboot eXecution Environment”) [1] booting,
or net booting, can be used to load an operating system
over the network without using the local hard drive.
While FreeBSD and Linux Operating Systems (OSes)
support a number of different PXE boot methods (including NFS, TFTP, HTTP, iSCSI and more), Windows only
provides support for iSCSI - a protocol for abstracting
remote storage as virtual block devices, similar to a hard
drive.
The benefits of PXE booting an OS include reduced
energy costs (fewer hard drives), easier maintenance
(reimage the PC without it being on) and flexible boot
options (have multiple OS options without needing to
repartition your hard drive).
This report will present a guide to setting up an iSCSI
backed PXE boot environment and installing Windows 7
to it. A Windows PreInstallation (PE) environment will
be used to load the iSCSI drive before beginning setup.
The changes to the process required for Windows XP
are detailed in Appendix A
The report is structured as follows: some background
is detailed in Section II; requirements and details of our
test bed are in Section III. Instructions on setting up
the required servers are in Section IV. Instructions on
configuring the PXE booting are in Section V. Creating
∗
Author was undertaking an IBL placement at CAIA when this
report was written
CAIA Technical Report 130226A
and testing the Windows PE are detailed in Section VI.
Installing to the iSCSI drive is covered in Section VII.
The report concludes with Section IX and an appendix.
II. BACKGROUND
A. DHCP
Dynamic Host Configuration Protocol’s (DHCP) [2]
primary purpose is to assign IP addresses and other
network configuration details to hosts. It is used in this
tutorial for the purposes of providing network and PXE
booting configuration details, including TFTP server
settings and configuration filenames.
B. TFTP
Trivial File Transfer Protocol (TFTP) [3] is a simple
protocol to transfer files. It is commonly used in PXE
scenarios because of its simplicity. The iPXE ROM and
configuration are stored on the TFTP server, and are
loaded by the PXE boot ROM on the Network Interface
Card (NIC).
C. iPXE
iPXE [4] provides advanced PXE functionality by
extending the range of boot options to include iSCSI
and other protocols. It can be flashed on to a NIC’s boot
ROM and used instead of the existing one or PXE booted
via TFTP.
Once iPXE is loaded, our DHCP will provide the
name of the configuration file, conf.ipxe. This file
is interpreted by iPXE. iPXE can also chainload another
executable file using this same method - including from a
HTTP or FTP URI, unlike a standard PXE environment.
D. iSCSI
SCSI (Small Computer System Interface) is a protocol
which allows a computer to communicate with directly
attached storage devices, such as hard drives and optical
drives. iSCSI [5] encapsulates the SCSI protocol within
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IP packets. iSCSI storage devices appear as a directly
attached disk.
The iSCSI client is called the iSCSI initiator, while
the iSCSI target refers to the storage device on the iSCSI
server. An iSCSI target does not need to be a physical
disk on the iSCSI server - it can be a file, a partition
or any block device. In this tutorial, a file is used as the
target, but this can be exchanged for any of the supported
storage mechanisms easily. This tutorial uses the istgt
iSCSI target software [6].
E. The boot process
At boot time, the PC operates in a mode that allows
iPXE to hook in to the BIOS and make the iSCSI drive
appear as a physical drive. The initial stages of the OS
are loaded while the PC remains in this mode. Once the
OS switches to “protected” mode, iPXE is no longer able
to operate in that manner, and is unloaded. When iPXE
is unloaded, the iSCSI drive is disconnected, and the OS
must initiate its own connection. Using information from
the iBFT (iSCSI Boot Firmware Table), which iPXE
populates during its execution, the OS re-connects the
iSCSI target and continues booting.
If the OS does not have iSCSI boot support, then
when it switches to protected mode it will completely
lose access to its boot disk and be unable to continue
booting.
Windows supports iSCSI booting, but only if iSCSI
is where Windows was initially installed to. To include
support for this within the Windows installation media,
Windows Automated Installation Kit (AIK) [7] is used.
•
•
•
Windows 7 installation media
inetd TFTP [10]
ISC DHCPD v4.2.4-P2 [11]
C. What we used
Client 1: HP Compaq DC7800. The internal hard drive
was blank. The PC has an onboard Intel gigabit NIC.
Server: HP Compaq DC7900, running PC-BSD 9.0RELEASE x64. All software except iPXE was installed
through the FreeBSD ports tree, which was up to date
as of 2012-12-20. iPXE was compiled on a Linux PC,
as it would not compile under FreeBSD. A pre-compiled
version is available at [8].
Figure 1 shows how the PCs are networked.
Figure 1.
Software used
III. R EQUIREMENTS
IV. S ERVER S ETUP
All configuration files referenced throughout this document have full examples available at [8]. Some lines
have been wrapped over multiple lines in this document.
If a line ends with a slash (\), it continues on the next
line.
If you do not control your network, you should ensure
that you isolate the testbed network from your usual
network. The tutorial involves setting up DHCP, which
can interfere with your existing network operation. In a
home environment, the worst case scenario is that some
PCs will not be able to access each other or the internet
until after you have removed your DHCP server from the
network. In many corporate environments, your network
port will be shut down if a DHCP server is detected.
However, an internet connection is temporarily needed
during the installation of software, as FreeBSD ports
require internet access to fetch content.
Our example test bed will use 10.0.0.0/24 as a
network and our server will be configured with an IP
address of 10.0.0.1.
A. Hardware
•
•
•
A Linux or FreeBSD server - the instructions cover
FreeBSD, but are easily adaptable to other BSDs or
Linuxes.
10GB or more of free disk space on the server
A PC or virtual machine running Windows 7
B. Software
•
•
•
iPXE v1.0.0 [9]
istgt v0.5, extra version 20121028 [6]
Windows 7 AIK [7] (and a Windows PC or VM to
use it on)
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A. DHCP
server isc-dhcpd onerestart.
1) Advanced DHCP configuration: The above conOn your server, start by installing the ISC DHCP
figuration
assumes that every PC on the network will
server. On FreeBSD, it is available as a port under net/isc-dhcp42-server. As root, install us- be netbooting from the same image. This presents two
ing cd /usr/ports/net/isc-dhcp42-server problems - the first is that multiple clients using the same
&& make install clean. The default options are NTFS partition simultaneously will result in significant
data corruption; the second is that you may not want
acceptable.
Once installed, open the configuration file - every device on your network netbooting - eg, some
Cisco devices treat the filename option as their con/usr/local/etc/dhcpd.conf .
The example simple configuration file is split in to figuration file, and complain about receving an invalid
two categories - subnet declarations, which start with a configuration file.
A PC will only try to netboot if it receives the
“subnet” line and contain everything within the following
braces; and the global section, which is everything that filename option from the DHCP server. Using a host
definition, the filename option can be conditionally
is not part of a subnet declaration.
Add the following subnet declaration anywhere within provided. Place the host definition at the end of the
DHCP configuration file, after the existing subnet decthe global section.
laration. Multiple host definitions may be specified in
subnet 10.0.0.0 netmask 255.255.255.0 { separate host definitions.
authoritative;
range 10.0.0.100 10.0.0.254;
host arbitrary-name {
if exists user-class and
hardware ethernet 11:22:33:44:55:66;
option user-class = iPXE
if exists user-class and
{
option user-class = iPXE
filename conf.ipxe;
{
}
filename conf.ipxe;
else
}
{
else
filename undionly.kpxe;
{
option routers 10.0.0.1;
filename undionly.kpxe;
}
}
next-server 10.0.0.1;
}
}
This
configuration
declares
a
subnet
(10.0.0.0/255.255.255.0), then states that the DHCP
server is authoritative for the network interface this
subnet is on. An authoritative server will ensure that all
DHCP discover requests from clients result in the client
being assigned an address. This is important if a client
has an old DHCP lease it attempts to renew.
The range directive specifies the inclusive range of
IP addresses that may be assigned to DHCP clients.
The if/else block tests for if the DHCP client is
iPXE or not and conditionally sets the filename directive.
This is covered in V. It also conditionally provides the
gateway (option routers) to clients. iPXE should not be
given a gateway unless the iSCSI target is not on the
same subnet. See Appendix B for more information.
The next-server directive dictates the TFTP
server to be used by a PXE client.
Restart the DHCP daemon using:
CAIA Technical Report 130226A
Then remove the filename lines from within the
subnet declaration.
This
host
definition
defines
the
host
arbitrary-name. It is good practice to have
the given name match the hostname of the PC. The
hardware-ethernet line gives the MAC address
of the PC that this host definition is for.
The same if/else block in the subnet declaration that
was controlling the filename option is now placed in
the host definition, performing the same task, but limiting
the scope of the filename option to only a single host
on the network.
B. TFTP
Now that our hosts can automatically configure themselves, they need somewhere to get images from. TFTP
is a simple file transfer protocol, commonly used to
“bootstrap” an OS by loading the kernel or another
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small, specialised, boot loader. We will be using it to
provide iPXE and its configuration file. iPXE gets the
address of the TFTP server from the DHCP server’s
next-server option.
inetd provides a TFTP server on both FreeBSD and
Linux. This is typically installed by default.
Open /etc/inetd.conf and find the line that begins “#tftp dgram udp”. Remove the # and ensure
the last parameter is “/tftpboot”.
Save the file, create the /tftpboot folder, chmod
444 /tftpboot and restart the inetd daemon using
service inetd onerestart.
C. istgt
istgt is an iSCSI server. It will act as an iSCSI
target for our net booted Windows.
On FreeBSD, istgt is available as a port
under net/istgt. As root, install using cd
/usr/ports/net/isgtg && sudo make
install clean. The default options are acceptable.
A file will be used to store our data. Create an empty
file of your desired size - we assume there is a /netboot
directory to store images in. We used 10GB for our
Windows 7 32 bit installation. Microsoft recommends
16GB for 32 bit and 20GB for 64 bit installations.
dd if=/dev/zero \
of=/netboot/windows7.img \
bs=10m count=1000
All of istgt’s configuration files are located
in
/usr/local/etc/istgt/
on
FreeBSD.
Copy
istgtcontrol.conf.sample
to
istgtcontrol.conf, then open it.
Every iSCSI drive has a unique name, called the
IQN (iSCSI Qualified Name). The TargetName in
istgtcontrol.conf sets the IQN of the disk.
Alter the TargetName line to be:
TargetName iqn.2012-12.com.example:windows7
’iqn’ indicates that it is an IQN formatted name.
’2012-12’ is the date the server was created.
’com.example’ is the Fully Qualified Domain Name
(FQDN) of the server, in reverse. ’windows7’ is an
arbitrary name for the disk. The first three fields form a
server identifier, and the fourth identifies the disk within
the server. The date and FQDN fields are a naming
convention only, and do not have any effect aside from
giving the disk a unique name. You may change the
IQN according to your environment, ensuring to change
the configuration accordingly wherever it is used.
Replace “localhost” on the line “Host
localhost” with your IP address.
CAIA Technical Report 130226A
Save and exit.
Copy istgt.conf.sample to istgt.conf, then open it.
Under the [Global] section, change the NodeBase
to iqn.2012-12.com.example
Under the [LogicalUnit1] section, change the
TargetName to windows7, then add the following
line, also in the [LogicalUnit1] section:
LUN0 Storage /netboot/windows7.img \
10737418240
The number at the end of the line is the size of the
image in bytes. You can confirm this by checking the
filesize through ls -l /netboot
Under [PortalGroup1], change the line Portal
DA1 192.168.2.1:3260 to reflect your IP address.
Likewise, under [InitiatorGroup1], change
Netmask 192.168.2.0/24 to reflect your network’s subnet - 10.0.0.0/24 in our example.
Save the file and start istgt.
If you have an OS that supports connecting to iSCSI,
you can try connecting to it now to test it. On Windows,
open a command prompt and try:
net start msiscsi
iscsicpl.exe
Then on the window that opens, enter the IP address
of the server in the box at the top and click the find
button next to it. It should automatically find and mount
the drive, and it should be visible in disk manager.
V. PXE SETUP
When a PC attempts to PXE boot, the boot ROM
obtains a network configuration from DHCP. Part of the
configuration can be boot information. The filename
option set in our DHCPd configuration file tells the boot
ROM which file to obtain from TFTP. The DHCP server
is configured to provide a different filename setting
depending on which user-class option is sent with
the DHCP request.
The default filename is undionly.kpxe - this is the
UNDI (Universal Network Driver Interface) version of
the iPXE image. There are card-specific versions of
iPXE, however UNDI is suitable for almost any network
card manufactured in the last decade.
A. Build iPXE
A pre-compiled version of iPXE is provided alongside
the example files [8]. If compiling iPXE, be aware that
at the time of writing it did not compile under FreeBSD
9.1-RELEASE or 10.0-CURRENT (Feb 2nd release)
due to a compiler segmentation fault. It was sucessfully
compiled under Linux (Ubuntu 12.04.1 x64)
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Create the iPXE image by checking out the latest
version from Git and compiling it:
git clone git://git.ipxe.org/ipxe.git
cd ipxe/src
make bin/undionly.kpxe
Transfer
ipxe/bin/undionly.kpxe
to
/tftpboot/ on the server.
You can optionally embed your configuration in to
iPXE by creating the configuration file (see next step)
and appending EMBED=conf.ipxe to the make line.
Any embedded configuration can still be overridden by
a valid filename DHCP parameter.
You can also install iPXE to your NICs Boot ROM,
negating the need for DHCP and TFTP. The procedure
is device specific and outside the scope of the tutorial.
B. iPXE configuration
The filename we provide to iPXE through DHCP
dictates its configuration file.
The example configuration file hooks the iSCSI drive
in to the iBFT, and returns control to the BIOS. Doing
this during iPXE execution enables the BIOS to be
aware of it, which is important for when the Windows
installation happens.
#!ipxe
set keep-san 1
sanhook --drive 0x80 \
iscsi:10.0.0.1::::iqn.2012-12.com.example:windows7
exit
keep-san makes it such that the iSCSI drive is kept
in the iBFT, even if no OS is found on it.
sanbook
initiates
the
iSCSI
connection
to the specified drive. In the drive address,
’iscsi’ identifies it as an iSCSI disk,
’10.0.0.1’ specifies the server IP address and
iqn.2012-12.com.example:windows7 is the
IQN set in istgt. The –drive 0x80 argument sets the
BIOS drive number.
exit gracefully exits and passes on to the next boot
device - either our installation media or the iSCSI disk.
iPXE supports menu creation, so it is possible to make
mounting the iSCSI disk optional. See Appendix C for
more information.
If you have issues booting the installation media in
Section VII, try changing the drive number of the iSCSI
disk to 0x81 or 0x82 using the --drive option of
sanhook.
1) Advanced iPXE configuration: If you followed
the steps in Section IV-A1 to make host-specific
DHCP configurations, you may also make hostspecific iPXE configurations. [12] shows how to
use the MAC address to dynamically configure your
CAIA Technical Report 130226A
iPXE environment using the ${net0/mac} or
${net0/mac:hexhyp} variables. You can use these
to load a host-specific configuration file with chain
http://10.0.0.1/boot.php?mac=${net0/mac}
and making the appropriate script on the web server.
VI. W INDOWS AIK
The Windows Automated Install Kit [7] allows system administrators to easily deploy customised images
of Windows to PCs and create “Preinstallion Environments”. Preinstallation environments (PEs) allow a user
to boot a lightweight Windows environment without
installing Windows. We will create our own PE with
the iSCSI drivers built in, such that Windows setup can
see the disk in order to install Windows to it. Note that
our Windows PE image is not a setup image itself, but
is merely the boot media we use. Once Windows PE is
loaded, we will launch setup from the normal Windows
installation media.
These steps are based on a Microsoft Technet article
[13].
Our example will use “i386” as the architecture. If
you are making a 64-bit OS image, you need to replace
i386 with “amd64” where ever it appears.
After download and installing the AIK from [7], open
a command prompt as an administrator.
cd \
mkdir winpe
cd c:\Program Files\Windows
AIK\Tools\PETools\
copype.cmd i386 c:\winpe\
This will create a winpe.wim image file
in c:\winpe\, as well as a number of
directories. Copy and rename winpe.wim to
c:\winpe\ISO\sources\boot.wim.
Copy
c:\Program Files\Windows
AIK\Tools\i386\bcdboot.exe
to
c:\winpe\ISO\
Copy
c:\Program Files\Windows
AIK\Tools\i386\oscdimg.exe
to
c:\winpe\Boot\
Copy
c:\Program Files\Windows
AIK\Tools\PETools\i386\etfsboot.com
to c:\winpe\Boot
Now we need to mount the boot.wim image and make
some modifications.
mkdir c:\mount
imagex /mountrw
c:\winpe\ISO\sources\boot.wim 1
c:\mount
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Copy the following files from a computer running
Windows 7 or Windows Server 2008 R2 to the same
location under c:\mount\. Make sure that the source
PC uses the same archicture (i386 or amd64) that your
image is:
\windows\System32
iscsicli.exe
iscsicpl.dll
iscsicpl.exe
iscsidsc.dll
iscsied.dll
iscsiexe.dll
iscsium.dll
iscsiwmi.dll
\windows\System32\Drivers
msiscsi.sys
\windows\System32\en-US
iscsicpl.dll.mui
iscsicpl.exe.mui
iscsidsc.dll.mui
iscsiexe.dll.mui
Obtain PE_Sys.reg and PE_Soft.reg from [8] - these
will make some modifications to the registry inside the
image.
Open
regedit.exe,
click
on
“HKEY_LOCAL_MACHINE”,
then
open
the
file menu and “Load Hive”. Open the file
c:\mount\windows\system32\config\software.
When asked for a name, enter PE_Soft. (the name is
important - do not use a different name). Repeat this
step, opening the System file in the same directory, and
calling it PE_Sys.
Merge the two .reg files obtained earlier into the
registry by double clicking them, then select PE_Soft,
then the file menu, and “Unload Hive”. Select PE_Sys
and “Unload Hive” again.
Close any Windows explorer windows, then unmount
the image using imagex /commit /unmount
c:\mount
Create the ISO file using:
cd \winpe\boot
oscdimg.exe -n -betfsboot.com \
c:\winpe\ISO c:\winpe\winpe.iso
Burn the ISO image to a CD. Make sure that you are
able to boot from it.
PE disc. Reboot, and wait for Windows PE to finish
loading. Since the first boot option is Network booting,
iPXE will load and mount the iSCSI drive, then hand
control back to the BIOS, which will then boot Windows
PE from the optical or USB media.
If the BIOS gives an error message about invalid
system disk or INT13, see Appendix E.
Once the WinPE environment has loaded, you will be
presented with a command prompt.
Figure 2.
In the command prompt, run “net start msiscsi”.
Figure 3.
Starting the Microsoft iSCSI service
Then type ’iscsicpl.exe’. If everything worked, a window will open and there will already be an entry in the
list of targets (as in Figure 4). If there isn’t, then reboot
and watch for any errors during iPXE execution. If there
are no errors, go back to the iPXE setup in Section V-B
and change the drive number of the iSCSI device.
VII. B OOTING AND INSTALLATION
Figure 4.
In your computer’s BIOS, set the boot order to boot
from the network, then from optical drive or USB, depending on your installation media. Insert the Windows
CAIA Technical Report 130226A
The initial state of the Windows PE
The iSCSI Control Panel
Remove the Windows PE disc and insert the Windows
7 installation disk. In the command prompt, change to
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the optical drive by entering “d:” and pressing enter.
Check that this is the right drive by doing “dir” and
ensuring setup.exe, boot\ and sources\ are in
the list, as in Figure 5. If not, try e:, f: and so on.
Figure 5.
If iPXE gives an error about the iSCSI target, make
sure istgt is running and that there are no typos in the
iPXE configuration file.
After iPXE finishes executing its configuration script,
it may give an error about “no more network
devices” - this is safe to ignore.
Before Windows is install, if no bootable optical
media is inserted you may get an invalid system
disk error after iPXE exits. If the invalid system
disk or an INT13 error message still appears when
bootable optical media is inserted later, see Appendix E.
The contents of the Windows installation disk
Enter “setup.exe” in to the command prompt, and
wait for the setup UI to load. Once it loads, continue
installation like you would for any normal Windows
installation. The iSCSI target will appear as a normal
hard drive in the drive selection step.
After setup finishes, it should reboot to your diskless
Windows installation.
VIII. T ROUBLESHOOTING
A. The server configuration
In the BIOS of your client, make sure network booting
is enabled and that it is the first in the boot order. Save
and exit.
If PXE is working, after the BIOS has completed
Power-On Self Test (POST) , you should see a screen
with text at the top that mentions a PXE Boot Agent, or
a Boot ROM, or similar (See Fig. 6). It should indicate
that it is then attempting to establish a link, then acquire
a DHCP address. If the DHCP request times out, make
sure that ISC-DHCPD is started, and that there are no
errors in /var/log/messages on the server.
If a DHCP address is successfully acquired, it should
then load iPXE. If iPXE does not load, check that the
“filename” parameter in the ISC-DHCP configuration
file matches the filename in /tftpboot/. Try downloading the file yourself by doing: cd /tmp; tftp
10.0.0.1, then enterting “get undionly.kpxe”.
If it times out, inetd is not running. If it gives you an access error, check the permissions on both /tftpboot/
and the files inside. It is fine for these files to be world
readable.
CAIA Technical Report 130226A
Figure 6.
An example successful PXE boot with iPXE
If Windows setup loads and cannot detect the iSCSI
drive, reboot and watch the boot process - make sure that
iPXE successfully regsiters the SAN device. To make
iPXE pause, edit the conf.ipxe file and insert ’prompt’
on a new line before exit.
IX. C ONCLUSIONS
This report has provided a tutorial on the steps required to boot Windows 7 and XP without a local disk.
ISC DHCPD, iPXE and TFTP are used to provision a
PXE boot environment, istgt is used as an iSCSI target
and the Windows Automated Installation Kit is used to
implement iSCSI support in to the Windows 7 installer.
Once completed, Windows 7 and XP are able to use
exclusively network attached storage to boot and operate.
R EFERENCES
[1] “Preboot Execution Environment (PXE) Specification.”
http://download.intel.com/design/archives/wfm/downloads/
pxespec.pdf. Accessed Feb 5th, 2013.
[2] R. Droms, “RFC 1531 - Dynamic Host Configuration Protocol.”
https://tools.ietf.org/html/rfc1531. Accessed Feb 5th, 2013.
[3] K. R. Sollins, “RFC 783 - TFTP Protocol (revision 2).” https:
//tools.ietf.org/html/rfc783. Accessed Feb 5th, 2013.
[4] “iPXE.” http://ipxe.org. Accessed Feb 5th, 2013.
[5] J. Satran, K. Meth, C. Sapuntzakis, M. Chadalapaka, and
E. Zeidner, “RFC 3720 .” http://www.ietf.org/rfc/rfc3720.txt.
Accessed 3rd Jan, 2013.
[6] “FreshPorts – net/istgt.” http://www.freshports.org/net/istgt/.
Accessed Feb 5th 2013.
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[7] “Download Windows (R) AIK for Windows (R) 7 from Official
Microsoft Download Center.” http://www.microsoft.com/en-us/
download/details.aspx?id=5753. Accessed 16th Dec, 2012.
[8] C. Holman, “Example configuration files and other resources.”
http://caia.swin.edu.au/tools/130226A/. Accessed 25th Feb,
2013.
[9] https://git.ipxe.org/ipxe.git/commit/
717279a294e414218deb1c89d33422b209574053.
Accessed
Dec 13th, 2012.
[10] “The
inetd
Super-Server.”
http://www.freebsd.org/doc/
handbook/network-inetd.html. Accessed Feb 5th 2013.
[11] “FreshPorts – net/isc-dhcp42-server.” http://www.freshports.
org/net/isc-dhcp42-server/. Accessed Feb 5th 2013.
[12] “[cfg:mac].” http://ipxe.org/cfg/mac. Accessed Jan 4th, 2013.
[13] “Creating, Validating, and Testing Boot Images.” http://technet.
microsoft.com/en-us/library/ee619769(WS.10).aspx. Accessed
16th Dec, 2012.
[14] “SAN
Boot
Conf
Installer,
0.9.7.”
http:
//git.etherboot.org/sanbootconf.git/blob/
60ed443b667412b0ce6f9b8173c6a1220c0728bd:/sanbootconf.
msi. Accessed 16th Dec, 2012.
[15] “Microsoft iSCSI Initiator Version 2.09.” http://www.microsoft.
com/en-au/download/details.aspx?id=18986.
Accessed 16th
Dec, 2012.
[16] “If you start a system from iSCSI, the gateway specified in
the iSCSI Boot solution will always be used by Windows to
communicate with the iSCSI Target.” http://support.microsoft.
com/kb/960104. Accessed 3rd Jan, 2013.
[17] G.
Armitage,
“Adding
Intel
PXE
Boot
under
FreeBSD/VirtualBox.” http://grenville.wordpress.com/2012/03/
18/adding-intel-pxe-boot-under-freebsdvirtualbox/. Accessed
16th Dec, 2012.
[18] “VirtualBox LAN boot ROM.” http://www.etherboot.org/wiki/
romburning/vbox. Accessed 16th Dec, 2012.
A PPENDIX
A. Altering the procedure for Windows XP
Start by installing Windows XP in to VirtualBox. Be
warned that while VirtualBox will create an expandable
virtual disk file that grows as more disk is used, the final
image we use will be as big as the capacity of the drive.
Once XP is installed, install both [14] and [15] - for
the second link, download the x64 or x86 version under
“Checked Build links for Boot Initiator Builds”.
Shutdown the XP Virtual Machine.
From the command line on the VirtualBox host, run:
qemu-img convert -f vmdk -O raw \
/path/to/existing-disk.vmdk \
new-disk.img
qemu-img is available in the FreeBSD port
emulators/qemu or on Ubuntu as the package
qemu.
The resulting new-disk.img file is the image that istgt
should be configured to use as its target in Section IV-C.
Follow the rest of the tutorial, skipping Sections VI and
VII.
CAIA Technical Report 130226A
B. Reasons for the static route for iSCSI in Windows 7
The configuration information for the iSCSI drive,
including the network configuration, is stored in the
iBFT (iSCSI Boot Firmware Table). Windows uses this
information to initiate its connection to the iSCSI target.
One of the assumptions that Windows makes is that
you will only ever have your iSCSI connection on a NIC
that is dedicated to iSCSI, and that if it is configured it
with a default router, it’s because the router is required to
access the iSCSI target [16]. Because of this assumption,
Windows will always add a static route to the iSCSI
target, via the default gateway that is in use at the time
the iSCSI connection is initiated. While the intention of
this static route is to ensure the iSCSI target is always
accessible, the consequence is that your iSCSI traffic
may end up being forwarded through your router and
back out on to the same LAN. This is far from ideal, for
example, if the router is a consumer ADSL modem or
if a wireless link is in the path to the router.
The workaround is to make the provision of a router
address conditional on the DHCP client not being iPXE,
as in the example DHCP configuration provided in
Section IV-A.
By making this change, iPXE does not have a gateway
configured when it inserts the configuration information
into the iBFT, therefore Windows will not add a static
route and will direct-connect to the iSCSI target. When
Windows loads its own networking stack, it will not send
iPXE as its user-class, so will be given the option
routers configuration and the windows networking
stack will operate as normal.
If a router is required to access the iSCSI target, then
the option routers line should be moved to outside
of the if/else block - after the next-server line, for
example.
C. Creating an iPXE menu
iPXE supports creating a menu. The menus are simple,
but adequate for providing choice in booting. They are
declared in the following format:
menu Title of the menu
item value Label of this item
item value2 Label of the second item
choose answer
One can then use the answer to direct the script to
a certain location. Here is an example menu script that
gives the option of mounting iSCSI or bypassing it:
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devices once the iSCSI drive is mounted. If Windows
menu Please choose your OS
item win7 Windows 7 (iSCSI)
is installed elsewhere (eg, in VMWare) instead, you can
item default Defer to next in boot order
boot Windows by changing sanhook to sanboot in the
choose --default default os && goto ${os}
:win7
iPXE configuration. sanboot immediately boots from the
set keep-san 1
sanhook iscsi:10.0.0.1::::iqn.2012-12.com.example:disk1iSCSI drive. sanhook will mount the drive, and wait for
exit
the BIOS to boot from it once the BIOS reaches it in its
:default
boot order. The latter allows you to boot from alternate
exit
D. iSCSI booting Windows in VirtualBox
VirtualBox supplies two different families of NICs
that it can emulate, Intel and AMD - Windows only
has drives for the Intel family. However, the Intel virtual
NICs do not come with a boot ROM, so this must be
installed manually. This blog post [17] details how to
configure VirtualBox with a boot ROM. Alternatively,
you can compile iPXE to be the boot ROM, by following
this article [18]. Note that, while the instructions are for
gPXE, they also valid for iPXE.
Also note that the tested version of VirtualBox (
4.1.22OSE ) will not try secondary boot devices (ie, hard
disk or optical media) once a PXE ROM has been loaded
(eg, iPXE). This is an important caveat, as the given
instructions rely on the BIOS to try subsequent boot
CAIA Technical Report 130226A
media (eg, a live CD) and still have the iSCSI drive
visible - this is a requirement to install Windows 7.
Windows XP installation is not affected by this, as XP
is installed using traditional methods, then the installation is modified to support iSCSI booting.
E. PCs that fail to continue booting after loading a PXE
Some PCs will not try further boot devices if a PXE
ROM executes then exits - such as how iPXE is operating
in this tutorial. This problem does not appear to affect
the majority of PCs. If this happens, try installing on
another computer. Windows must be installed straight to
iSCSI, but once installed, may be booted on a different
PC.
Installing to PCs that exhibit this behaviour is not
within the scope of this report.
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